Locking means for an over-centre fastener

ABSTRACT

A locking means for an over-centre fastener for preventing unintentional opening of a lever of the fastener, comprises a spring ( 30 ) attached to the lever ( 21   a ) and abutment means ( 31 ) associated with a the stationary part ( 20 ) of the fastener. The spring ( 30 ) has one end attached to the lever ( 21   a ) and an opposite, movable end thereof forms engagement means ( 34   a ) engaging the abutment means ( 31 ) in a closed position of the fastener. Said opposite end of the spring is formed with guide means ( 34   a   , 34   c ) guiding movement of said opposite end of the spring relative to the lever ( 21   a ).

The present invention concerns a locking means for an over-centrefastener according to the preamble of claim 1.

Over-centre fasteners (also denominated toggle fasteners or latches) arecommonly used for securing—and often clamping—two objects together, suchas keeping a lid in a closed position on a box or case. A first part ofthe fastener, referred to as a striker and often having a hook-likeshape, is attached to one of the objects. A base member of the otherpart of the fastener is attached to the other object.

An inherent feature of over-centre fasteners is the self-lockingproperty when closed and under load. At occasions, it may occur that theload is permanently or temporarily decreased, such as due to vibrationor shock, and in such cases the operating lever of the fastener may beset in motion to an extent that it passes the dead point of theover-centre mechanism. The consequence is not only that the clampingforce of the fastener is lost, but may even involve damage or injury.

EP 1 179 393 A1 discloses a large-scale clamp mechanism mechanicallyresembling an over-centre fastener, but not having the self-lockingproperty thereof. Thus, in order to hold the clamp mechanism in a closedposition, its operating handle carries a spring loaded lock memberengaging a latch extending from a stationary base member. The lockmember is released from its engagement with the latch by manuallydepressing it against the spring force, thereby enabling raising of thehandle and release of the clamp mechanism.

Although useful also for locking a true over-centre fastener, this priorart device has the apparent drawback that, applied to a normal-sizedover-centre fastener, its lock member would be cumbersome andobstructive to the easiness of operating the fastener, since it extendssubstantially perpendicularly downwards from a mid-portion of thehandle.

The present invention has as its object to provide a manually releasablespring loaded locking means that sets aside the aforementioned drawback.

Thus, there is provided a locking means for an over-centre fastener forpreventing unintentional opening of the fastener, including manuallyreleasable spring-action retaining means acting between a movable leverand a stationary part of the fastener. The spring action retaining meanscomprise a spring attached to the lever, and an abutment means isassociated with the stationary part. The spring has one end attached tothe lever and an opposite, movable end thereof forming engagement meansis adapted to engage the abutment means in a closed position of thefastener, said opposite end of the spring being formed with guide meansguiding movement of said opposite end of the spring relative to thelever.

Embodiments of the present invention will now be described, referencebeing made to the accompanying drawings, wherein:

FIG. 1 is a side view of an over-centre fastener according to apreferred embodiment of the present invention shown in a open position;

FIG. 2 is a plan view of the fastener of FIG. 1;

FIG. 3 is a side view of the fastener according to FIGS. 1 and 2 in aclosed position;

FIG. 4 is a plan view of the fastener as shown in FIG. 3;

FIG. 5 is a section at an enlarged scale taken along line V-V in FIG. 4;

FIG. 6 is a section at an enlarged scale taken along line VI-VI in FIG.2;

FIG. 7 is a side view of a leaf spring used in the embodiment of FIGS.1-6 shown in the scale of FIGS. 5 and 6;

FIG. 8 is a side view of an over-centre fastener having a wire spring asa retaining means and being shown in a closed position;

FIG. 9 is a plan view of the fastener of FIG. 8;

FIG. 10 is a plan view of the fastener of FIGS. 8 and 9 showing the wirespring in its released position; and

FIG. 11 is a section taken along line XI-XI in FIG. 9.

The over-centre fasteners according to the present invention are basedon a conventional fastener. Such fastener will be described withreference to FIGS. 1-4. It comprises a base plate 20 to be fixed to oneobject A to be clamped to another object B, a lever 21 and an engagementmember 22. The lever 21 is swingable about rivets 23 a, 23 b engaged inspaced brackets 20 a, 20 b protruding from the base plate 20. A firstend 22 a of the engagement member 22 is threaded and engages internalthreads of a cylindrical body 24 which is linked to the lever 21 at adistance from the rivets 23 a, 23 b. More precisely, the cylindricalbody 24 is carried between spaced legs 21 a, 21 b of the lever 21 so asto be rotational about stub shafts 25 engaged in the spaced legs. A freeend of the engagement member 22 is formed with an eye 22 b forengagement with a hook-like end 26′ of a striker 26 attached to objectB. Often, there is a further bracket 27 integral with the base plate andhaving a hole 28 which is aligned with a hole 29 in the lever 21 in itsclosed state for the purpose of locking the lever to the base plate bymeans of a padlock.

Apart from such positive locking, in a conventional over-centre fastenerbeing in its closed state according to FIG. 3 and being under clampingtension, substantially only the force from the engaging member directedinto the rotational centre of the cylindrical body 24 prevents the lever21 from passing over the dead-point and releasing the clamping force.

To prevent this, the present invention provides a manually releasablesnap-lock mechanism arranged between the stationary base plate 20 andthe lever 21.

A first, preferred embodiment of such mechanism is shown in FIGS. 1-7.It includes a leaf spring 30, carried by the lever 21 and beingseparately shown in FIG. 7, and an engagement surface 31 associated withthe base plate 20, in this case formed on the bracket 27.

The leaf spring 30 is elongate and its main plane extends-in its normal,unstrained state along the inner side of leg 21 a. It has a hole 32 atone of its ends and a further hole 33 at a distance therefrom. This endof the spring is fixed to the leg 21 a by being clamped between theinner end of the leg and, on one hand, the clinched inner end 23 a′ ofrivet 23 a extending through hole 32, and, on the other hand, thecylindrical body 24, the stub shaft 25 of which extends through the hole33.

The free end of the leaf spring carries along its upper edge 30 a anintegral flap 34. A substantially horizontal portion 34 a thereofextends at substantially 90° from the main plane of the spring so as toextend above and beyond the leg 21 a of the lever 21 (FIGS. 4 and 5) adistance substantially equal to or somewhat greater that the width ofthe leg 21 a. The free end of the horizontal portion 34 a is bent downto form a substantially vertical portion 34 b, and its free end isfurther inwardly bent to form a lower, substantially horizontal portion30 c extending below the leg 21 a. As will be seen in FIG. 5, the freeedge 30 c of the lower horizontal portion 34 c leaves a small space tothe lower edge 30 b of the leaf spring that is less than the width ofthe leg 21 a.

In the closed position of the lever 21 shown in FIGS. 3-5, the upperhorizontal portion 34 a is located underneath the engagement surface 31of the bracket 27 and prevents upward movement of the lever as seenparticularly in FIGS. 3-5.

To release the lever, the flap 34 is pressed to the left in FIG. 5 so asto resiliently move its horizontal portion 34 a from its positionunderneath the engagement surface 31. In the position of the flap 34shown in FIG. 6, in which its substantially vertical portion 34 b abutsthe exterior side of leg 21 a, the lever is released and is free to beopened, whereupon the leaf spring may regain its unloaded position alongthe leg 21 a. When again closed, a bevelled cam surface 35 of thebracket 27 engages the lower horizontal portion 34 c and forces the leafspring to deflect inwardly until the upper horizontal portion 34 a hasreached a position just before that of FIG. 6 and is free to regain itsunstrained locking position. The movements of the leaf spring are guidedby the upper and lower horizontal portion 34 a, 34 c sliding against theupper and lower surfaces, respectively, of leg 21 a.

In a second embodiment of the present invention shown in FIGS. 8-11 awire spring 36 is used as a retaining means. One end of a straight mainportion 36 a of the spring is bent at 90° and an eye 36 b is formed atthe free end thereof. A rivet 37 attaches the spring to the leg 21 b ofthe lever 21. The straight main portion 36 a of the spring extendsperpendicularly from the leg 21 b and passes beyond the leg 21 a. Thefree end of the spring is bent to form a U-shaped, manually releasablecatch 36 c straddling the leg 21 a. In the closed position of the lever21 shown in FIGS. 8, 9 and 11, an upper leg 36 e of the catch engages anotch 38 in the bracket 27′ in this embodiment being located between thelegs 21 a, 21 b of the lever 21. To release the lever, the catch ispressed downwardly in FIGS. 9 and 10. Movement of the catch is guided byits two opposed legs 36 d, 36 e straddling the leg 21 a of the lever.

1. A locking means for an over-centre fastener for preventingunintentional opening of the fastener, including manually releasablesnap-action retaining means (30, 34; 36) between a movable lever (21)and a stationary part (20, 27) of the fastener, said retaining meanscomprising a spring (30; 36) attached to the lever (21 a; 21 b) andabutment means (31; 38) associated with the stationary part (20, 27),characterized in that the spring (30) has one end attached to the lever(21 a) and an opposite, movable end thereof forming engagement means (34a; 36 a) adapted to engage the abutment means (31; 38) in a closedposition of the fastener, said opposite end of the spring being formedwith guide means (34 a, 34 c; 36 d, 36 e) guiding movement of saidopposite end of the spring relative to the lever (21 a).
 2. The lockingmeans according to claim 1, characterized in that the spring is a leafspring (30).
 3. The locking means according to claim 1, characterized inthat the spring is a wire spring (36).
 4. The locking means according toclaim 2 , characterized in that said guide means comprise at least oneportion (34 a, 34 c; 36, 36 d) of said spring (30; 36) bent to encompassa portion of said lever.
 5. The locking means according to claim 3,characterized in that said guide means comprise at least one portion (34a, 34 c; 36, 36 d) of said spring (30; 36) bent to encompass a portionof said lever.